Document authentification

ABSTRACT

A method producing authenticatable documents by incorporating a fluorescent organometallic complex in the toner or in the paper in which the fluorescent organometallic complex gives off light with a characteristic spectrum when exposed to UV light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of the filing date of internationalapplication PCT/GB02/04761 filed Oct. 21, 2002, which claims the benefitof the filing date of United Kingdom application no. 0126065.2 filedOct. 31, 2001.

The present invention relates to a method of producing authenticateddocuments which are hard to counterfeit.

The problem of marking various objects with identifying marks or codes,which are invisible in normal light, has been addressed several times inthe prior art. For instance, U.S. Pat. No. 3,507,655 describes andclaims a process for producing marking invisible in natural light butvisible in ultraviolet on a plastic substrate exhibiting fluorescentproperties, but when exposed to a source of intense optical radiationthrough a stencil bearing the desired marking pattern, the radiationcauses a change in the fluorescence in the substrate in the irradiatedarea, so that the marking is invisible in ordinary light, but visibleunder UV illumination.

None of these systems, however, are successfully applicable to normalprinting or copying systems and apparatus and they all involveoperations additional to printing or copying, causing increasedmanufacturing complication and costs.

WO 793471 discloses a method for the labelling of printed documentsproduced by solid toner apparatus, such as a laser printer or a copyingmachine, with a material the presence of which can be detected usingspectrophotometric techniques, and thus can be used to verify theauthenticity of the document. The labelling is invisible to the nakedeye and does not interfere with the contents of the printed document.

The process of verifying the authenticity of the document involves theexcitation of the marked toner with light in the range of 150-800 nm,and the measurement of the light emitted from the excited marked tonerby a spectrometer. The document inspected must emit light having aspectrum identical to that preset for the specific document Thus, anemission of light with the wrong spectrum will not identify the documentas being authentic.

A range of fluorescent dies are disclosed and a preferred dye isN,N′-Ditridecyl-3,4,9,10-perylenetetracarboxyhc diimide.

French Patent 1471367 and U.S. Pat. No. 4,833,311 disclose a method forthe use of rare earth fluorescent chelates to protect documents againstcounterfeiting and to the detection counterfeit documents.

In this method the rare earth fluorescent chelate is dissolved in avarnish which is used to print a plastic foil which is cut into strips,e.g. 1 mm wide which are introduced into security paper in the form ofthreads. Alternatively fibres, such as polyamide fibres, containing therare earth fluorescent chelates are produced, dried and added to paperpulp to produce security paper. In normal light the fibres arecolourless, but when excited by ultraviolet light the rare earthfluorescent chelates will fluoresce and emit light of a specificwavelength or wavelength characteristic of the rare earth fluorescentchelates. The emission spectrum is dependant on the temperature and inprior art methods disclosed the detection apparatus is equipped with aspectrofluorimeter to accurately check, in qualitative and quantitativemanner, the emitted fluorescent wavelengths as a function of thetemperature of the document being authenticated. Again it may include anelectro-optical assembly with suitable optical filters to detect thechange in the fluorescent wavelengths as a function of temperature andto display directly the result of the double check.

Depending on the kind of coolant used, for instance liquid helium,liquid nitrogen, dry ice or other, the apparatus receiving the documentsbeing authenticated may be open and constantly resupplied, or closed.The cooled trough furthermore may be replaced by a jet of coolant byatomizing e.g. liquid nitrogen onto the document. This requirement touse a range of temperatures is a serious disadvantage and requires theuse of expensive cooling apparatus, in addition the fluorescentmaterials disclosed do not have strong photoluminescent properties andrequire the use of expensive fluorimeters to detect the colour and relyon subject identification of colour by a user.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIGS. 1, 2 a and 2 b are formulae drawings representing types ofcompounds Lp in accordance with chemical formula (XVIII) of theinvention.

FIG. 3 is a formula drawing representing another type of compound Lpbased on bathophen in accordance with the invention.

FIGS. 4 a to 4 l are formulae drawings representing other types ofcompounds Lp in accordance with this invention.

FIGS. 5 a to 5 f are formulae drawings representing still other types ofcompounds Lp in accordance with this invention.

FIGS. 6 a to 6 e, 7 a to 7 f and 8 a to 8 h are formulae drawingsrepresenting yet other types of compounds Lp in accordance with thisinvention.

FIG. 9 shows formulae drawings representing polyamines in accordancewith this invention shown in their acetic acid form.

DESCRIPTION OF PREFERRED EMBODIMENTS

We have now discovered that a range of organometallic complexes can beused to produce readily authenticatable material which can beauthenticated at room temperature and which complexes give a strongemission which can be digitized.

The material can be paper, cloth, a plastic material and any material onwhich the organometallic complexes can be deposited.

In one embodiment of the invention there is provided a method ofproducing an image on a document in which the paper, or the ink, toneror other material used to form the image incorporates a fluorescentmetal organic complex of the type set out below.

The invention also provides a toner composition which comprises amixture of toner and a fluorescent metal organic complex.

The invention further provides materials documents produced using such acomposition.

The fluorescent compounds which can be used in the present invention areof general formula (Lα)_(n)M where M is a rare earth, lanthanide or anactinide, Lα is an organic complex and n is the valence state of M.

Other fluorescent compounds which can be used in the present inventionare of formula(Lα)_(n) >M←Lpwhere Lα and Lp are organic ligands, M is a rare earth, transitionmetal, lanthanide or an actinide and n is the valence state of the metalM. The ligands Lα can be the same or different and there can be aplurality of ligands Lp which can be the same or different.

For example (L₁)(L₂)(L₃)(L . . . )M (Lp) where M is a rare earth,transition metal, lanthanide or an actinide and (L₁)(L₂)(L₃)(L . . . )are the same or different organic complexes and (Lp) is a neutralligand. The total charge of the ligands (L₁)(L₂)(L₃)(L . . . ) is equalto the valence state of the metal M. Where there are 3 groups Lα whichcorresponds to the III valence state of M the complex has the formula(L₁)(L₂)(L₃)M (Lp) and the different groups (L₁)(L₂)(L₃) may be the sameor different

Lp can be monodentate, bidentate or polydentate and there can be one ormore ligands Lp.

Preferably M is metal ion having an unfilled inner shell and thepreferred metals are selected from Sm(III), Eu(II), Eu(III), Tb(III),Dy(III), Yb(III), Lu(III), Gd(III), Gd(III) U(III), Tm(III), Ce(III),Pr(III), Nd(III), Pm(III), Dy(III), Ho(III), Er(III), Yb(III) and morepreferably Eu(III), Tb(III), Dy(III), Gd(III), Er(III), Yt(III).

Further fluorescent compounds which can be used in the present inventionare of general formula (Lα)_(n)M₁M₂ where M₁ is the same as M above, M₂is a non rare earth metal, Lα is a as above and n is the combinedvalence state of M₁ and M₂. The complex can also comprise one or moreneutral ligands Lp so the complex has the general formula (Lα)_(n) M₁M₂(Lp), where Lp is as above. The metal M₂ can be any metal which is not arare earth, transition metal, lanthanide or an actinide examples ofmetals which can be used include lithium, sodium, potassium, rubidium,caesium, beryllium, magnesium, calcium, strontium, barium, copper (I),copper (II), silver, gold, zinc, cadmium, boron, aluminium, gallium,indium, germanium, tin (II), tin (IV), antimony (II), antimony (IV),lead (II), lead (IV) and metals of the first, second and third groups oftransition metals in different valence states e.g. manganese, iron,ruthenium, osmium, cobalt, nickel, palladium(II), palladium(IV),platinum(II), platinum(IV), cadmium, chromium. titanium, vanadium,zirconium, tantalum, molybdenum, rhodium, iridium, titanium, niobium,scandium, yttrium.

For example (L₁)(L₂)(L₃)(L . . . )M (Lp) where M is a rare earth,transition metal, lanthanide or an actinide and (L₁)(L₂)(L₃)(L . . . )and (Lp) are the same or different organic complexes.

Further organometallic complexes which can be used in the presentinvention are binuclear, trinuclear and polynuclear organometalliccomplexes e.g. of formula (Lm)_(x)M₁←M₂(Ln)_(y) e.g.

where L is a bridging ligand and where M₁ is a rare earth metal and M₂is M₁ or a non rare earth metal, Lm and Ln are the same or differentorganic ligands Lα as defined above, x is the valence state of M₁ and yis the valence state of M₂.

In these complexes there can be a metal to metal bond or there can beone or more bridging ligands between M₁ and M₂ and the groups Lm and Lncan be the same or different.

By trinuclear is meant there are three rare earth metals joined by ametal to metal bond i.e. of formula

where M₁, M₂ and M₃ are the same or different rare earth metals and Lm,Ln and Lp are organic ligands Lα and x is the valence state of M₁, y isthe valence state of M₂ and z is the valence state of M₃. Lp can be thesame as Lm and Ln or different.

The rare earth metals and the non rare earth metals can be joinedtogether by a metal to metal bond and/or via an intermediate bridgingatom, ligand or molecular group.

For example the metals can be linked by bridging ligands e.g.

where L is a bridging ligand

By polynuclear is meant there are more than three metals joined by metalto metal bonds and/or via intermediate ligands

where M₁, M₂, M₃ and M₄ are rare earth metals and L is a bridgingligand.

Preferably Lα is selected from β diketones such as those of formulae

wherein the formulas (I), (II) and (III) above are respectively referredto as “formula (I)”, “formula (II)” and “formula (III)” hereinafter, andfurther where R₁, R₂ and R₃ can be the same or different and areselected from hydrogen, and substituted and unsubstituted hydrocarbylgroups such as substituted and unsubstituted aliphatic groups,substituted and unsubstituted aromatic, heterocyclic and polycyclic ringstructures, fluorocarbons such as trifluoryl methyl groups, halogenssuch as fluorine or thiophenyl groups; R₁, R₂ and R₃ can also formsubstituted and unsubstituted fused aromatic, heterocyclic andpolycyclic ring structures and can be copolymerisable with a monomere.g. styrene. X is Se, S or O, Y can be hydrogen, substituted orunsubstituted hydrocarbyl groups, such as substituted and unsubstitutedaromatic, heterocyclic and polycyclic ring structures, fluorine,fluorocarbons such as trifluoryl methyl groups, halogens such asfluorine or thiophenyl groups or nitrile.

Examples of R₁ and/or R₂ and/or R₃ include aliphatic, aromatic andheterocyclic alkoxy, aryloxy and carboxy groups, substituted andsubstituted phenyl, fluorophenyl, biphenyl, phenanthrene, anthracene,naphthyl and fluorene groups alkyl groups such as t-butyl, heterocyclicgroups such as carbazole.

Some of the different groups Lα may also be the same or differentcharged groups such as carboxylate groups so that the group L₁ can be asdefined above and the groups L₂, L₃ . . . can be charged groups such as

wherein the formula (IV) above is referred to hereinafter as “formula(IV)”, and further where R is R₁ as defined above or the groups L₁, L₂can be as defined above and L₃ . . . etc. are other charged groups.

R₁, R₂ and R₃ can also be

wherein the formula (V) above is referred to hereinafter as “formula(V)”, and further where X is O, S, Se or NH.

A preferred moiety R₁ is trifluoromethyl CF₃ and examples of suchdiketones are, banzoyltrifluoroacetone, p-chlorobenzoyltrifluoroacetone,p-bromotrifluoroacetone, p-phenyltrifluoroacetone,1-naphthoyltrifluoroacetone, 2-naphthoyltrifluoroacetone,2-phenathoyltrifluoroacetone, 3-phenanthoyltrifluoroacetone,9-anthroyltrifluoroacetonetrifluoroacetone, cinnamoyltrifluoroacetone,and 2-thenoyltrifluoroacetone.

The different groups Lα may be the same or different ligands of formulae

wherein the formula (VI) above is referred to hereinafter as “formula(VI)”, and further where X is O, S or Se and R₁, R₂ and R₃ are as above.

The different groups Lα may be the same or different quinolatederivatives such as

wherein the formula (VII) above is referred to hereinafter as “formula(VII)”, and further where R is hydrocarbyl, aliphatic, aromatic orheterocyclic carboxy, aryloxy, hydroxy or alkoxy e.g. the 8 hydroxyquinolate derivatives or

wherein the formula (VIII) above is referred to hereinafter as “formula(VIII)”, and further where R, R₁ and R₂ are as above or are H or F e.g.R₁ and R₂ are alkyl or alkoxy groups

wherein the formula (IX) above is referred to hereinafter as “formula(IX)”, and further as stated above the different groups Lα may also bethe same or different carboxylate groups e.g.

wherein the formula (X) above is referred to hereinafter as “formula(X)”, and further where R₅ is a substituted or unsubstituted aromatic,polycyclic or heterocyclic ring a polypyridyl group, R₅ can also be a2-ethyl hexyl group so L_(n) is 2-ethylvesanoate or r % can be a chairstructure so that L_(n) is 2-acetyl cyclohexanoate or Lα can be

where R is as above e.g. alkyl, allenyl, amino or a fused ring such as acyclic or polycyclic ring.

The different groups Lα may also be

(XIVa)  (XV)

wherein the formulas (XIVa), (XV), (XVII) and (XVIIa) above arerespectively referred to as “formula (XIVa)”, “formula (XV)”, “formula(XVII)” and “formula (XVIIa)” hereinafter, and further where R, R₁ andR₂ are as above.

The groups L_(P) can be selected from

wherein the formula (XVIII) above is referred to hereinafter as “formula(XVIII)”

Where each Ph which can be the same or different and can be a phenyl(OPNP) or a substituted phenyl group, other substituted or unsubstitutedaromatic group, a substituted or unsubstituted heterocyclic orpolycyclic group, a substituted or unsubstituted fused aromatic groupsuch as a naphthyl, anthracene, phenanthrene or pyrene group. Thesubstituents can be for example an alkyl, aralkyl, alkoxy, aromatic,heterocyclic, polycyclic group, halogen such as fluorine, cyano, amino.Substituted amino etc. Examples are given in FIGS. 1 and 2 of thedrawings where R, R₁, R₂, R₃ and R₄ can be the same or different and areselected from hydrogen, hydrocarbyl groups, substituted andunsubstituted aromatic, heterocyclic and polycyclic ring structures,fluorocarbons such as trifluoryl methyl groups, halogens such asfluorine or thiophenyl groups; R, R₁, R₂, R₃ and R₄ can also formsubstituted and unsubstituted fused aromatic, heterocyclic andpolycyclic ring structures and can be copolymerisable with a monomere.g. styrene. R, R₁, R₂, R₃ and R₄ can also be unsaturated alkylenegroups such as vinyl groups or groups—C—CH₂═CH₂—Rwhere R is as above.

L_(p) can also be compounds of formulae

wherein the formulas (XVIV), (XX) and (XXI) above are respectivelyreferred to as “formula (XVIV)”, “formula (XIX)” and “formula (XXI)”hereinafter, and further where R₁, R₂ and R₃ are as referred to above,for example bathophen shown in FIG. 3 of the drawings in which R is asabove or

wherein the formulas (XXII) and (XXIII) above are respectively referredto as “formula (XXII)” and “formula (XXIII)” hereinafter, and furtherwhere R₁, R₂ and R₃ are as referred to above.

L_(p) can also be

wherein the formulas (XXIV) and (XXV) above are respectively referred toas “formula (XXIV)” and “formula (XXV)” hereinafter, and further wherePh is as above.

Other examples of L_(p) chelates are as shown in FIG. 4 and fluorene andfluorene derivatives e.g. a shown in FIG. 5 and compounds of formulae asshown as shown in FIGS. 6 to 8.

Specific examples of Lα and Lp are tripyridyl and TMHD, and TMHDcomplexes, α, α′, α″ tripyridyl, crown ethers, cyclans, cryptansphthalocyanans, porphoryins ethylene diamine tetramine (EDTA), DCTA,DTPA and TTHA. Where TMHD is 2,2,6,6-tetramethyl-3,5-heptanedionato andOPNP is diphenylphosphonimide triphenyl phosphorane. The formulae of thepolyamines are shown in FIG. 9 in their acetic acid form.

Other fluorescent materials which can be used include metal quinolatessuch as lithium quinolate, and non rare earth metal complexes such asaluminium, magnesium, zinc and scandium complexes such as complexes ofβ-diketones e.g. Tris -(1,3-diphenyl-1-3-propanedione) (DBM) andsuitable metal complexes are Al(DBM)₃. Zn(DBM)₂ and Mg(DBM)₂. Sc(DBM)₃etc.

Other fluorescent materials which can be used include the metalcomplexes of formula

wherein the formula (XXVI) above is referred to hereinafter as “formula(XXVI)” where M is a metal other than a rare earth, a transition metal,a lanthanide or an actinide; n is the valency of M; R₁, R₂ and R₃ whichmay be the same or different are selected from hydrogen, hydrocarbylgroups, substituted and unsubstituted aliphatic groups substituted andunsubstituted aromatic, heterocyclic and polycyclic ring structures,fluorocarbons such as trifluoryl methyl groups, halogens such asfluorine or thiophenyl groups or nitrile; R₁, and R₃ can also be formring structures and R₁, R₂ and R₃ can be copolymerisable with a monomere.g. styrene. Preferably M is aluminium and R₃ is a phenyl orsubstituted phenyl group.

The organometallic fluorescent compounds used in the present inventionhave a unique spectrum and can have more than one peak so that eachcomplex can have a unique colour. By mixing more than one compoundtogether a fluorescent spectrum can be produced which is virtuallyimpossible to reproduce. A form of the process by which toner coloursand labelling fluorescents may be associated into toner composition, isdescribed in WO 793471 and comprises the following steps; introducingthe labelling compound into an organic solvent, e.g. ethyl alcohol,whereby to produce a first suspension/solution of said labellingcompound in said organic solvent; applying a strong sonification for atime sufficient to produce a uniform suspension/solution of saidlabelling compound particles in said first solution, whereby a moderateheating, typically to about 40° C., is obtained; adding distilled waterto said first suspension/solution to an amount that does not cause theprecipitation of the labelling compound, whereby to obtain a secondsuspension/solution of said labelling compound in a mixture of theorganic solvent and water, adding the toner particles to said secondsuspension/solution while stirring; diluting with distilled water to asufficient extent to cause homogenous precipitation of said labellingcompound onto said toner particles, whereby to produce labelled tonerparticles; stirring the above for an additional few hours, during whichgenerally some organic solvent evaporates, causing further precipitationof the labelling compound.; filtering said labelled toner particles fromthe liquid phase of said suspension; drying the filtrate under vacuum;and milling and sieving the dried filtrate.

For the fluorescent compounds of the present invention preferredsolvents are chloromethanes such as dichloromethane and trichloromethaneand toluene etc. typically the concentration in the solvent is from 1%to 10% by volume.

It is important to avoid defects in the process, for instance, the tonerparticles will be totally covered and will change their colour and theirelectrostatic properties; or numerous fluorescent crystallites will beformed, that are not bound to toner particles and will not betransferred to the print substrate during the electrostatic process ofthe printing.

When multiple applications of different labelling fluorescents isdesired, one carries out the aforesaid procedure twice or more, oncewith each labelling fluorescent, or carry out the aforesaid process onceby mixing with the water suspension of the toner colours a solution inorganic solvent of the mixture of the desired labeling fluorescents.

However, other methods can be used for producing the toner compositioncontaining the toner colours and the labelling fluorescents. This can bedone, for instance, by mixing them in solid, finely particulate form bymelt coating etc.

The fluorescent compound or compounds used should, as has been said,preferably be colourless and, therefore they may be consideredcolourless toners. They should also be such as not substantially toalter the colours of the toner colours, although some alteration istolerable and can be taken into account. Likewise, it is desirable thatthe colourless toner should not affect substantially the electrostaticand thermal properties of the toner colours, and therefore nor interferewith their deposition on the paper.

When the rare earth chelate is to be incorporated in a security paper inthe form of a thread or threads, the process described in U.S. Pat. No.4,833,311 can be used.

At the printer a varnish containing the rare earth metal chelate isplaced into a trough and a propylene film is printed. This printed filmis cut into strips constituting security threads incorporated into asecurity paper during its manufacture.

In U.S. Pat. No. 4,833,311 a process is disclosed in which a rare earthmetal chelate or mixture of rare earth metal chelates which emitsfluorescent light at a different wavelength at low temperatures is usedin order to authenticate a document and a fluorimeter sensitive in thevisible and infrared spectra analyzes the fluorescent light and itsvariation in relation to the temperature of the security paper being UVexcited at both ambient and low temperatures. This apparatus may beconnected to another memorizing the particular desired rate ofalternation and capable of comparing between read-out rate of the movingsecurity paper to be authenticated and the stored rate and thereby toprovide a go/no-go response in this automated authentication procedureof a security paper.

In its most simple version the apparatus detecting the fluorescence ofthe chelates will be a UV exciting source having a support for thedocuments and a trough holding a low-temperature liquid. The document tobe authenticated is presented manually or automatically to thisapparatus, exposed to a source of ultra-violet, and it will thereforeemit the intrinsic fluorescence of the rare earth at room temperature,whereupon, still being UV excited, it is immersed in the low temperaturetrough it will emit the intrinsic fluorescence at the low temperature.Once so authenticated, the document is removed from the apparatus andanother document is then subjected to the same authentication test.However this need to vary the temperature and the use of an expensivefluorimeter are disadvantages of this process.

With the chelates used in the present invention a much strongerfluorescent emission is obtained and a more simple detector can be usedat room temperature the detector can operate by shining ultra violetlight on the document and detecting the fluorescent light emitted byphotoluminescence. With rare earth chelates used there is a very strongemission which enables lower power detectors to be used which are muchcheaper than the detectors which have had to be used with the priormethods.

The spectrum of photoluminescent complexes, especially rare earthchelates, will have a main peak emission frequency which will correspondto the colour of the emission and will also have much smaller side peaksat frequencies different from the main frequency. The size of these sidepeaks is at least partially dependant on the nature of the ligands usedin the complexes and, by using a detector which measures the size ofthese peaks, it is possible to obtain a series of number whichcorrespond to the ratio of the size of these peaks and the size of themain emission and which will be unique to the particular complex used.There are a very large number of ligand combinations which can be usedand so it is possible to provide distinct identification for a verylarge number of different documents.

When a mixture of photoluminescent complexes are used, each complex willhave a peak emission at a specific frequency of a specific size, byhaving a detector which can measure the size of these peaks it ispossible to obtain a series of number which correspond to the ratio ofthe size of these peaks and which will be unique to the particularmixture of complexes used. There are a very large number of chelatecombinations which can be used and so it is possible to provide distinctidentification for a very large number of different documents.

In either situation the detector can produce a series of numbers for thedocument being tested which are the ratios referred to and this seriesof numbers will be unique for the particular complex or complexes used.It is thus a simple matter for an operator to compare this series ofnumbers to the series of numbers which should be obtained if thedocument is genuine without the need for subjective recognition ofcolours in the prior used methods.

As the marking can be invisible the invention is useful for theidentification and authentification of items which could becounterfeited such as items made from ceramics, cloth, plastics, metaletc. and articles made from such materials such as trainers, and otherclothing items, Videos, CDs so that it can be ascertained if the articleis genuine and, if it originated from a source within the producer'sorganisation, the location of the source of the item or material can beidentified.

1. A method of authenticating or identifying an article that has beenmarked with or incorporates a fluorescent complex that, when exposed toultra-violet light, produces a main emission peak at a main emissionfrequency of the complex and a set of side peaks at frequenciesdifferent from the main emission frequency of the complex, said complexbeing selected from the group consisting of: A. type (i) materialshaving the general chemical formula(Lα)_(n) >M←Lp where: M is an element selected from the group consistingof lanthanide series elements and actinide series elements, n is thevalence state of the element M, Lα is an organic complex which consistsof a single ligand or multiple ligands which may be the same ordifferent, and Lp is an organic complex which consists of a singleligand or multiple ligands which may be the same or different; and, B.type (ii) materials having the general chemical formula(Lα)_(n)M₁M₂ where: M₁ is an element selected from the group consistingof rare earth elements, transition elements, lanthanide series elementsand actinide series elements, M₂ is a non rare earth metal, Lα is anorganic complex which consists of a single ligand or multiple ligandswhich may be the same or different, and n is the combined valence stateof M₁ and M₂, said method comprising the steps of: (a) calculating afirst series of numbers corresponding to the ratios of the sizes of theside peaks for the fluorescent complex relative to the size of the mainemission peak for the fluorescent complex; (b) shining ultra-violetlight onto the article and thereby producing a combination of a mainemission peak for the article at a main emission frequency and a set ofsmaller side peaks for the article at frequencies different from themain frequency; (c) determining the size of the main emission peak forthe article at the main emission frequency of the fluorescent complex,and also determining the sizes of the side peaks for the article atleast one or more frequencies different from the main emissionfrequency; (d) calculating a second series of numbers corresponding tothe ratios of the sizes of the side peaks for the article relative tothe size of the main emission peak for the article, said numbers beingunique to a the fluorescent complex; and, (e) authenticating oridentifying the article by comparing the similarity of the ratios in thesecond series of numbers obtained for the article with the correspondingratios in the first series of numbers.
 2. The method according to claim1 wherein the fluorescent complex is a type (ii) material, and furtherwherein the element M₂ of that material is a metal which is not a rareearth element, transition element, lanthanide series element or actinideseries element.
 3. A method according to claim 1 wherein the fluorescentcomplex is a type (ii) material, and further wherein the metal M₂ ofthat material is selected from the group consisting of lithium, sodium,potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium,barium, copper (I), copper (II), silver, gold, zinc, cadmium, boron,aluminum, gallium, indium, germanium, tin (II), tin (IV), antimony (II),antimony (IV), lead (II), lead (IV) and metals of the first, second andthird groups of transition metals in different valence states includingmanganese, iron, ruthenium, osmium, cobalt, nickel, palladium(II),palladium(IV), platinum(II), platinum(IV), chromium, titanium, vanadium,zirconium, tantalum, molybdenum, rhodium, iridium, titanium, niobium,scandium and yttrium.
 4. A method according to claim 1 wherein thearticle is a paper document and further wherein the paper incorporatesthe fluorescent complex.
 5. The method of claim 1 wherein the article isa paper document and further wherein the fluorescent complex isincorporated in the paper in the form of material strips containing thefluorescent complex.
 6. The method of claim 1 wherein the article is apaper document and further wherein visible markings on the documentcomprise a medium which incorporates the fluorescent complex.
 7. Amethod of authenticating or identifying an article that has been markedwith or incorporates a mixture of fluorescent complexes that, whenexposed to ultra-violet light, produces main emission peaks at the mainemission frequencies of the complexes and sets of side peaks atfrequencies different from the main emission frequencies of thecomplexes, said complexes being selected from the group consisting of:A. type (i) materials having the general chemical formula(Lα)_(n) >M←Lp where: M is an element selected from the group consistingof lanthanide series elements and actinide series elements, n is thevalence state of the element M, Lα is an organic complex which consistsof a single ligand or multiple ligands which may be the same ordifferent, and Lp is an organic complex which consists of a singleligand or multiple ligands which may be the same or different; and, B.type (ii) materials having the general chemical formula(Lα)_(n)M₁M₂ where: M₁ is an element selected from the group consistingof rare earth elements, transition elements, lanthanide series elementsand actinide series elements, M₂ is a non rare earth metal, Lα is anorganic complex which consists of a single ligand or multiple ligandswhich may be the same or different, and n is the combined valence stateof M₁ and M₂, said method comprising the steps of: (a) calculating afirst series of numbers corresponding to the ratios of the side peaksfor the fluorescent complexes relative to the sizes of the main emissionpeaks for the fluorescent complexes; (b) shining ultra-violet light ontothe article and thereby producing for each complex a combination of amain emission peak for the article at a main emission frequency and aset of smaller side peaks for the article at frequencies different fromthe main frequency; (c) determining the sizes of the main emission peaksfor the article at the main emission frequency of each fluorescentcomplex; (d) calculating a second series of numbers corresponding to theratios of the sizes of the main emission peaks for the article, saidnumbers being unique to the particular mixture of fluorescent complexes;and, (e) authenticating or identifying the article by comparing thesimilarity of the ratios in the second series of numbers obtained forthe article with the corresponding ratios in the first series ofnumbers.
 8. The method according to claim 7 wherein one of thefluorescent complexes is a type (ii) material, and further wherein theelement M₂ of that material is a metal which is not a rare earthelement, transition element, lanthanide series element or actinideseries element.
 9. A method according to claim 7 wherein one of thefluorescent complexes is a type (ii) material, and further wherein themetal M₂ of that materials is selected from the group consisting oflithium, sodium, potassium, rubidium, caesium, beryllium, magnesium,calcium, strontium, barium, copper (I), copper (II), silver, gold, zinc,cadmium, boron, aluminum, gallium, indium, germanium, tin (II), tin(IV), antimony (II), antimony (IV), lead (II), lead (IV) and metals ofthe first, second and third groups of transition metals in differentvalence states including manganese, iron, ruthenium, osmium, cobalt,nickel, palladium(II), palladium(IV), platinum(II), platinum(IV),chromium, titanium, vanadium, zirconium, tantalum, molybdenum, rhodium,iridium, titanium, niobium, scandium and yttrium.
 10. A method accordingto claim 7 wherein the article is a paper document that has been markedwith the mixture of fluorescent complexes by the steps of: at a printer,placing a varnish containing the fluorescent complexes into a trough;printing a propylene film containing the fluorescent complexes to form aprinted film; cutting the printed film into strips constituting securitythreads; and, incorporating a plurality of the security threads into thepaper during its manufacture.
 11. A method according to claim 7 whereinthe article is a paper document and further wherein the paperincorporates the mixture of fluorescent complexes.
 12. A methodaccording to claim 11 wherein the fluorescent complexes are incorporatedinto the paper by means of security threads produced by a printingprocess using a toner or varnish containing the fluorescent complexes.13. The method of claim 7 wherein the article is a paper document andfurther wherein the mixture of fluorescent complexes is incorporated inthe paper in the form of material strips containing the mixture offluorescent complexes.
 14. The method of claim 7 wherein the article isa paper document and further wherein visible markings on the documentcomprise a medium which incorporates the mixture of fluorescentcomplexes.
 15. A method of authenticating or identifying an article thathas been marked with or incorporates one or a mixture of fluorescentcomplexes that, when exposed to ultra-violet light, produces mainemission peaks at the main emission frequencies of the complexes andsets of side peaks at frequencies different from the main emissionfrequencies of the complexes, said complexes being selected from thegroup consisting of materials having the general chemical formula(Lα)_(n)M₁M₂(Lp) where: Lα is an organic complex which consists of asingle ligand or multiple ligands which may be the same or different, Lpis an organic complex which consists of a single ligand or multipleligands which may be the same or different; M₁ is an element selectedfrom the group consisting of rare earth elements, transition elements,lanthanide series elements and actinide series elements, M₂ is a nonrare earth metal, and n is the combined valence state of M₁ and M₂,where a single fluorescent complex was used for marking the article,said method comprising the steps of: (a) calculating a first series ofnumbers corresponding to the ratios of the sizes of the side peaks forthe fluorescent complex relative to the size of the main emission peakfor the fluorescent complex; (b) shining ultra-violet light onto thearticle and thereby producing a combination of a main emission peak forthe article at a main emission frequency and a set of smaller side peaksfor the article at frequencies different from the main frequency; (c)determining the size of the main emission peak for the article at themain emission frequency of the fluorescent complex, and also determiningthe sizes of the side peaks for the article at least one or morefrequencies different from the main emission frequency; (d) calculatinga second series of numbers corresponding to the ratios of the sizes ofthe side peaks for the article relative to the size of the main emissionpeak for the article, said numbers being unique to the fluorescentcomplex; and, (e) authenticating or identifying the article by comparingthe similarity of the ratios in the second series of numbers obtainedfor the article with the corresponding ratios in the first series ofnumbers; or, alternatively, where a mixture of fluorescent complexes wasused for marking the article, said method comprising the steps of: (f)calculating a first series of numbers corresponding to the ratios of thesizes of the side peaks for the fluorescent complexes relative to thesizes of the main emission peaks for the fluorescent complexes; (g)shining ultra-violet light onto the article and thereby producing foreach complex a combination of a main emission peak for the article at amain emission frequency and a set of smaller side peaks for the articleat frequencies different from the main frequency; (h) determining thesizes of the main emission peaks for the article at the main emissionfrequency of each fluorescent complex; (i) calculating a second seriesof numbers corresponding to the ratios of the sizes of the main emissionpeaks for the article, said numbers being unique to a particular mixtureof fluorescent complexes; and, (j) authenticating or identifying thearticle by comparing the similarity of the ratios in the second seriesof numbers obtained for the article with the corresponding ratios in thefirst series of numbers.
 16. A method according to claim 15 wherein thearticle is a paper document and further wherein the paper incorporatesthe fluorescent complex or complexes.
 17. The method of claim 15 whereinthe article is a paper document and further wherein the fluorescentcomplex or complexes is or are incorporated in the paper in the form ofmaterial strips containing the fluorescent complex or complexes.
 18. Themethod of claim 15 wherein the article is a paper document and furtherwherein visible markings on the document comprise a medium whichincorporates the fluorescent complex or complexes.
 19. A method ofauthenticating or identifying an article that has been marked with orincorporates one or a mixture of fluorescent complexes that, whenexposed to ultra-violet light, produces main emission peaks at the mainemission frequencies of the complexes and sets of side peaks atfrequencies different from the main emission frequencies of thecomplexes, said complexes being selected from the group consisting ofmaterials having one of the general chemical formulas:

where L is a bridging ligand and where M₁ is a rare earth element and M₂is either the same as M₁ or a non rare earth element, Lm and Ln are thesame or different organic ligands, x is the valence state of M₁, and yis the valence state of M₂;

where, in chemical formulas (iii) and (iv), M₁, M₂ and M₃ are the sameor different rare earth elements, Lm, Ln and Lp are organic ligands, xis the valence state of M₁, y is the valence state of M₂, and z is thevalence state of M₃, further wherein Lp can be the same as Lm and L_(n)or different;

where, in chemical formulas (v) and (vi), L is a bridging ligand wherebyrare earth elements and non rare earth elements are joined together by ametal-to-metal bond and/or via an intermediate bridging atom, ligand ormolecular group, and wherein at least three metals are joined bymetal-to-metal bonds and/or via intermediate ligands, where a singlefluorescent complex was used for marking the article, said methodcomprising the steps of: (a) calculating a first series of numberscorresponding to the ratios of the sizes of the side peaks for thefluorescent complex relative to the size of the main emission peak forthe fluorescent complex; (b) shining ultra-violet light onto the articleand thereby producing a combination of a main emission peak for thearticle at a main emission frequency and a set of smaller side peaks forthe article at frequencies different from the main frequency; (c)determining the size of the main emission peak for the article at themain emission frequency of the fluorescent complex, and also determiningthe sizes of the side peaks for the article at least one or morefrequencies different from the main emission frequency; (d) calculatinga second series of numbers corresponding to the ratios of the sizes ofthe side peaks for the article relative to the size of the main emissionpeak for the article, said numbers being unique to the fluorescentcomplex; and, (e) authenticating or identifying the article by comparingthe similarity of the ratios in the second series of numbers obtainedfor the article with the corresponding ratios in the first series ofnumbers; or, alternatively, where a mixture of fluorescent complexes wasused for marking the article, said method comprising the steps of: (f)calculating a first series of numbers corresponding to the ratios of thesizes of the side peaks for the fluorescent complexes relative to thesizes of the main emission peaks for the fluorescent complexes; (g)shining ultra-violet light onto the article and thereby producing foreach complex a combination of a main emission peak for the article at amain emission frequency and a set of smaller side peaks for the articleat frequencies different from the main frequency; (h) determining thesizes of the main emission peaks for the article at the main emissionfrequency of each fluorescent complex; (i) calculating a second seriesof numbers corresponding to the ratios of the sizes of the main emissionpeaks for the article, said numbers being unique to a particular mixtureof fluorescent complexes; and, (j) authenticating or identifying thearticle by comparing the similarity of the ratios in the second seriesof numbers obtained for the article with the corresponding ratios in thefirst series of numbers.
 20. The method according to claim 19 wherein,in the formulas (i), (ii), (v) and (vi), the element M₂ is a metal whichis not a rare earth element, transition element, lanthanide serieselement or actinide series element.
 21. A method according to claim 19wherein the metal M₂ is selected from the group consisting of lithium,sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium,strontium, barium, copper (I), copper (II), silver, gold, zinc, cadmium,boron, aluminum, gallium, indium, germanium, tin (II), tin (IV),antimony (II), antimony (IV), lead (II), lead (IV) and metals of thefirst, second and third groups of transition metals in different valencestates including manganese, iron, ruthenium, osmium, cobalt, nickel,palladium(II), palladium(IV), platinum(II), platinum(IV), chromium,titanium, vanadium, zirconium, tantalum, molybdenum, rhodium, iridium,titanium, niobium, scandium and yttrium.
 22. A method according to claim19 wherein the article is a paper document and further wherein the paperincorporates the fluorescent complex or complexes.
 23. The method ofclaim 19 wherein the article is a paper document and further wherein thefluorescent complex or complexes is or are incorporated in the paper inthe form of material strips containing the fluorescent complex orcomplexes.
 24. The method of claim 19 wherein the article is a paperdocument and further wherein visible markings on the document comprise amedium which incorporates the fluorescent complex or complexes.
 25. Amethod of authenticating or identifying an article that has been markedwith or incorporates a fluorescent complex which gives a strong emissionwhich can be digitized and that, when exposed to ultra-violet light,produces a main emission peak at a main emission frequency of thecomplex and a set of side peaks at frequencies different from the mainemission frequency of the complex, said complex being selected from thegroup consisting of: A. type (i) materials having the general chemicalformula(Lα)_(n) >M←Lp where: M is an element selected from the group consistingof lanthanide series elements and actinide series elements, n is thevalence state of the element M, Lα is an organic complex which consistsof a single ligand or multiple ligands which may be the same ordifferent, and Lp is an organic complex which consists of a singleligand or multiple ligands which may be the same or different; and, B.type (ii) materials having the general chemical formula(Lα)_(n)M₁M₂ where: M₁ is an element selected from the group consistingof rare earth elements, transition elements, lanthanide series elementsand actinide series elements, M₂ is a non rare earth metal, Lα is anorganic complex which consists of a single ligand or multiple ligandswhich may be the same or different, and n is the combined valence stateof M₁ and M₂, said method comprising the following steps all carried outat about room temperature: (a) calculating a first series of numberscorresponding to the ratios of the sizes of the side peaks for thefluorescent complex relative to the size of the main emission peak forthe fluorescent complex; (b) shining ultra-violet light onto the articleand thereby producing a combination of a main emission peak for thearticle at a main emission frequency and a set of smaller side peaks forthe article at frequencies different from the main frequency; (c)determining the size of the main emission peak for the article at themain emission frequency of the fluorescent complex, and also determiningthe sizes of the side peaks for the article at least one or morefrequencies different from the main emission frequency; (d) calculatinga second series of numbers corresponding to the ratios of the sizes ofthe side peaks for the article relative to the size of the main emissionpeak for the article, said numbers being unique to the fluorescentcomplex; and, (e) authenticating or identifying the article by comparingthe similarity of the ratios in the second series of numbers obtainedfor the article with the corresponding ratios in the first series ofnumbers.
 26. A method of authenticating or identifying an article thathas been marked with or incorporates a mixture of fluorescent complexeswhich gives a strong emission which can be digitized and that, whenexposed to ultra-violet light, produces main emission peaks at the mainemission frequencies of the complexes and sets of side peaks atfrequencies different from the main emission frequencies of thecomplexes, said complexes being selected from the group consisting of:A. type (i) materials having the general chemical formula(Lα)_(n) >M←Lp where: M is an element selected from the group consistingof lanthanide series elements and actinide series elements, n is thevalence state of the element M, Lα is an organic complex which consistsof a single ligand or multiple ligands which may be the same ordifferent, and Lp is an organic complex which consists of a singleligand or multiple ligands which may be the same or different; and, B.type (ii) materials having the general chemical formula(Lα)_(n)M₁M₂ where: M₁ is an element selected from the group consistingof rare earth elements, transition elements, lanthanide series elementsand actinide series elements, M₂ is a non rare earth metal, Lα is anorganic complex which consists of a single ligand or multiple ligandswhich may be the same or different, and n is the combined valence stateof M₁ and M₂, said method comprising the following steps all carried outat about room temperature: (a) calculating a first series of numberscorresponding to the ratios of the sizes of the side peaks for thefluorescent complexes relative to the sizes of the main emission peaksfor the fluorescent complexes; (b) shining ultra-violet light onto thearticle and thereby producing for each complex a combination of a mainemission peak for the article at a main emission frequency and a set ofsmaller side peaks for the article at frequencies different from themain frequency; (c) determining the sizes of the main emission peaks forthe article at the main emission frequency of each fluorescent complex;(d) calculating a second series of numbers corresponding to the ratiosof the sizes of the main emission peaks for the article, said numbersbeing unique to a particular mixture of fluorescent complexes; and, (e)authenticating or identifying the article by comparing the similarity ofthe ratios in the second series of numbers obtained for the article withthe corresponding ratios in the first series of numbers.
 27. A method ofauthenticating or identifying an article that has been marked with orincorporates one or a mixture of fluorescent complexes which gives astrong emission which can be digitized and that, when exposed toultra-violet light, produces main emission peaks at the main emissionfrequencies of the complexes and sets of side peaks at frequenciesdifferent from the main emission frequencies of the complexes, saidcomplexes being selected from the group consisting of materials havingthe general chemical formula(Lα)_(n)M₁M₂(Lp) where: Lα is an organic complex which consists of asingle ligand or multiple ligands which may be the same or different, Lpis an organic complex which consists of a single ligand or multipleligands which may be the same or different; M₁ is an element selectedfrom the group consisting of rare earth elements, transition elements,lanthanide series elements and actinide series elements, M₂ is a nonrare earth metal, and n is the combined valence state of M₁ and M₂,where a single fluorescent complex was used for marking the article,said method comprising the following steps all carried out at about roomtemperature: (a) calculating a first series of numbers corresponding tothe ratios of the sizes of the side peaks for the fluorescent complexrelative to the size of the main emission peak for the fluorescentcomplex; (b) shining ultra-violet light onto the article and therebyproducing a combination of a main emission peak for the article at amain emission frequency and a set of smaller side peaks for the articleat frequencies different from the main frequency; (c) determining thesize of the main emission peak for the article at the main emissionfrequency of the fluorescent complex, and also determining the sizes ofthe side peaks for the article at least one or more frequenciesdifferent from the main emission frequency; (d) calculating a secondseries of numbers corresponding to the ratios of the sizes of the sidepeaks for the article relative to the size of the main emission peak forthe article, said numbers being unique to the fluorescent complex; and,(e) authenticating or identifying the article by comparing thesimilarity of the ratios in the second series of numbers obtained forthe article with the corresponding ratios in the first series ofnumbers; or, alternatively, where a mixture of fluorescent complexes wasused for marking the article, said method comprising the following stepsall carried out at about room temperature: (f) calculating a firstseries of numbers corresponding to the ratios of the sizes of the sidepeaks for the fluorescent complexes relative to the sizes of the mainemission peaks for the fluorescent complexes; (g) shining ultra-violetlight onto the article and thereby producing for each complex acombination of a main emission peak for the article at a main emissionfrequency and a set of smaller side peaks for the article at frequenciesdifferent from the main frequency; (h) determining the sizes of the mainemission peaks for the article at the main emission frequency of eachfluorescent complex; (i) calculating a series of numbers correspondingto the ratios of the sizes of the main emission peaks for the article,said numbers being unique to a particular mixture of fluorescentcomplexes; and, (j) authenticating or identifying the article bycomparing the similarity of the ratios in the second series of numbersobtained for the article with the corresponding ratios in the firstseries of numbers.
 28. A method of authenticating or identifying anarticle that has been marked with or incorporates one or a mixture offluorescent complexes which gives a strong emission which can bedigitized and that, when exposed to ultra-violet light, produces mainemission peaks at the main emission frequencies of the complexes andsets of side peaks at frequencies different from the main emissionfrequencies of the complexes, said complexes being selected from thegroup consisting of materials having one of the general chemicalformulas:

where L is a bridging ligand and where M₁ is a rare earth element and M₂is either the same as M₁ or a non rare earth element, Lm and Ln are thesame or different organic ligands, x is the valence state of M₁, and yis the valence state of M₂;

where, in chemical formulas (iii) and (iv), M₁, M₂ and M₃ are the sameor different rare earth elements, Lm, Ln and Lp are organic ligands, xis the valence state of M₁, y is the valence state of M₂, and z is thevalence state of M₃, further wherein Lp can be the same as Lm and Ln ordifferent;

where, in chemical formulas (v) and (vi), L is a bridging ligand wherebyrare earth elements and non rare earth elements are joined together by ametal-to-metal bond and/or via an intermediate bridging atom, ligand ormolecular group, and wherein at least three metals are joined bymetal-to-metal bonds and/or via intermediate ligands, where a singlefluorescent complex was used for marking the article, said methodcomprising the following steps all carried out at about roomtemperature: (a) calculating a first series of numbers corresponding tothe ratios of the sizes of the side peaks for the fluorescent complexrelative to the size of the main emission peak for the fluorescentcomplex; (b) shining ultra-violet light onto the article and therebyproducing a combination of a main emission peak for the article at amain emission frequency and a set of smaller side peaks for the articleat frequencies different from the main frequency; (c) determining thesize of the main emission peak for the article at the main emissionfrequency of the fluorescent complex, and also determining the sizes ofthe side peaks for the article at least one or more frequenciesdifferent from the main emission frequency; (d) calculating a secondseries of numbers corresponding to the ratios of the sizes of the sidepeaks for the article relative to the size of the main emission peak forthe article, said numbers being unique to the fluorescent complex; and,(e) authenticating or identifying the article by comparing thesimilarity of the ratios in the second series of numbers obtained forthe article with the corresponding ratios in the first series ofnumbers; or, alternatively, where a mixture of fluorescent complexes wasused for marking the article, said method comprising the following stepsall carried out at about room temperature: (f) calculating a firstseries of numbers corresponding to the ratios of the sizes of the sidepeaks for the fluorescent complexes relative to the sizes of the mainemission peaks for the fluorescent complexes; (g) shining ultra-violetlight onto the article and thereby producing for each complex acombination of a main emission peak for the article at a main emissionfrequency and a set of smaller side peaks for the article at frequenciesdifferent from the main frequency; (h) determining the sizes of the mainemission peaks for the article at the main emission frequency of eachfluorescent complex; (i) calculating a second series of numberscorresponding to the ratios of the sizes of the main emission peaks forthe article, said numbers being unique to a particular mixture offluorescent complexes; and, (j) authenticating or identifying thearticle by comparing the similarity of the ratios in the second seriesof numbers obtained for the article with the corresponding ratios in thefirst series of numbers.